The present invention relates to a tape drive apparatus and particularly to an improved pinch roller. In tape playback and recording apparatus, particularly inexpensive systems utilized primarily in the consumer market for the recording and playback of magnetic tape and incorporating reel-to-reel, cassette or cartridge-type tapes, the tape drive is accomplished by means of a driven capstan which comprises a shaft against which the tape is forcibly held by a pinch roller compressibly positioned against the side of the tape opposite the capstan. Typically, the pinch roller itself is not driven but is free wheeling and the speed regulated capstan drives the tape on only one side. In such systems, the takeup mechanism may provide a signficant portion of the drive for transporting the tape across the playback head.
In order to maintain the tape in a vertically aligned position with respect to the tape head and the capstan, the pinch roller typically is crowned such that the flat tape will ride to the crest of the crowned roller and stay at such position. The crowning of the pinch roller, however, prevents effective positive engagement of the roller with the capstan, thus the tape will be driven only on the capstan side.
In cassette tape systems, frequently the resistance of the tape to being moved across the playback head caused by momentary sticking of the reels within the cassette or other momentary frictional contact of the tape within the cassette itself, causes speed changes of the tape across the playback head and which results in undesirable fluctuations of the audio output signal from the tape playback system. If recording, the problem will record the signal applied at a varying speed causing the same effect once played back at the desired speed.
In existing cassette-type tape recorders and playback systems, the cassette takeup spindle includes a slip clutch which is typically set within a range of 35-60 grams pull on the tape with the norm being 50 grams. If the slip is set too low, the tape can run past the capstan and accumulate on the takeup reel side fouling the system. If the slip clutch is set at too high a pull, it tends to pull the tape through the capstan and the capstan is ineffective in regulating the tape speed, thus causing the audio distortion.
Additionally, in manually operated systems such as described in my copending application entitled MANUAL TAPE APPARATUS, filed June 6, 1975, Ser. No. 584,465; (the disclosure of which is incorporated herein by reference) it is desirable to provide generating means in conjunction with the manual drive apparatus. The generating means coupled to the capstan drive requires relatively high speed for efficient generation of power for the device. With the present invention, the capstan diameter can be reduced in size and still maintain effective tape speed control and thereby the capstan can be rotated at a faster speed for a given tape speed, thus improving the generation of power for the amplifier portion of the system.